Radio frames in Long Term Evolution (LTE) systems and LTE-Advanced (LTE-A) systems include frame structures in a Frequency Division Duplex (FDD) mode and a Time Division Duplex (TDD) mode. FIG. 1 is a schematic diagram of a frame structure in related LTE/LTE-A FDD systems. As shown in FIG. 1, a radio frame of 10 ms consists of twenty slots numbered 0-19, each having a length of 0.5 ms, slots 2i and 2i+1 forming a subframe i with a length of 1 ms. FIG. 2 is a schematic diagram of a frame structure in related LTE/LTE-A TDD systems. As shown in FIG. 2, a radio frame of 10 ms consists of two half frames each having a length of 5 ms, a half frame includes 5 subframes each having a length of 1 ms, and a subframe i is defined as 2 slots 2i and 2i+1 each having a length of 0.5 ms.
In the two frame structures described above, for normal cyclic prefix (CP), one slot contains seven symbols each having a length of 66.7 μm, wherein the CP length of the first symbol is 5.21 μs, and the length of each of the remaining 6 symbols is 4.69 μs; for extended cyclic prefix, one slot contains six symbols, the CP length of each of which is 16.67 μs. The supported uplink and downlink configuration is shown as in Table 1.
TABLE 1uplink and downlink configuration tableDownlink -Uplink -uplinkdownlinkswitchingconfig-pointSubframe numberurationperiod012345678905msDSUUUDSUUU15msDSUUDDSUUD25msDSUDDDSUDD310msDSUUUDDDDD410msDSUUDDDDDD510msDSUDDDDDDD65msDSUUUDSUUD
For each subframe in one radio frame, “D” represents a subframe dedicated to downlink transmission, “U” represents a subframe dedicated to uplink transmission, “S” represents a special subframe which contains three portions, Downlink Pilot Time Slot (DwPTS), Guard Period (GP) and Uplink Pilot Time Slot (UpPTS).
In an LTE system, an HARQ process refers to that when a sending end needs to transmit data, a receiving end allocates information required in transmission, such as frequency domain resources, packet information, etc., to the sending end through downlink signaling. The sending end sends data according to the information while storing the data into its own buffer for retransmission. The receiving end detects the data after receiving the data, and sends an acknowledgement (ACK) to the sending end if the data are received correctly. The sending end clears the buffer memory, which is used in this transmission, after receiving the ACK, and ends this transmission. If the data are not received correctly, then a non-acknowledgement (NACK) is sent to the sending end and packets which are not received correctly are stored into the buffer memory of the receiving end. After the sending end has received the NACK information, it extracts the data from its own buffer memory and retransmits the data in a specific packet format in corresponding subframes and corresponding frequent domain positions. The retransmitted packets, after being received by the receiving end, are combined with the packets which are not received correctly and are detected once more. The above process is repeated until the data are received correctly or a retransmission times exceeds the maximum transmission times threshold.
In an LTE/LTE-A system, there is following specification regarding to PDSCH scheduling in downlink HARQ, i.e., regarding to scheduling of downlink HARQ: UE detects the PDCCH on subframe n and resolves the PDSCH of the current subframe according to information of the PDCCH.
In an LTE/LTE-A FDD system, there is the following timing rule regarding to the PUCCH corresponding to the HARQ-ACK of the PDSCH sent in the downlink HARQ, i.e., the following specification regarding to a timing relationship of the downlink HARQ: UE detects PDSCH transmission on subframe n or indicates the PDCCH of the downlink SPS release and transmits the corresponding HARQ-ACK response on subframe n+4. In an LTE/LTE-A TDD system, there is the following specification regarding to a timing relationship of the downlink HARQ: UE detects PDSCH transmission on subframe n-k or indicates the PDCCH of the downlink SPS release and transmits the corresponding HARQ-ACK response on uplink subframe n, wherein k belongs to K, values of which are as shown in table 2.
TABLE 2values of K in different uplink and downlink configurationsUplink -downlinkconfig-Subframe number nuration01234567890——6—4——6—41——7, 64———7, 64—2——8, 7, 4,————8, 7,——64, 63——7, 6, 116, 55, 4—————4——12, 8, 7,6, 5,——————114, 75——13, 12, 9,———————8, 7, 5,4, 11, 66——775——77—
In an LTE system, for example a Frequency Division Duplex (FDD) system, because of a one-to-one correspondence between uplink and downlink subframes, the UE will feed back the ACK/NACK response information of 1 bit when the PDSCH contains only one transmission block, and the UE will feed back the ACK/NACK response information of 2 bits when the PDSCH contains two transmission blocks, and the UE will send the ACK/NACK response information of ½ bit using a PUCCH format 1a/1b. In a Time Division Duplex (FDD) system, because there is no one-to-one correspondence between uplink and downlink subframes, the ACK/NACK response information corresponding to a plurality of downlink subframes will be sent on the PUCCH of one uplink subframe, wherein a set of downlink subframes corresponding to the uplink subframe form a “bundling window”. There are two methods for sending the ACK/NACK response information. One is bundling method, the key idea of which is to perform logical AND operation on the ACK/NACK response information, which is required to be fed back in the uplink subframe, of a transmission block corresponding to each of the downlink subframes. If there are 2 transmission blocks in one downlink subframe, UE will feed back the ACK/NACK response information of 2 bits, and if there is only one transmission block in each of the subframes, UE will feed back the ACK/NACK response information of 1 bit, and the UE will send the ACK/NACK response information of ½ bit using the PUCCH format 1a/1b. The other method is multiplexing with channel selection method, the key idea of which is to use different PUCCHs and different modulation symbols on the channels to represent different feedback states of the downlink subframe, which is required to be fed back in the uplink subframe. If there are a plurality of transmission blocks in the downlink subframes, logical AND operation (spatial bundling) will be performed on the ACK/NACK information fed back by the plurality of transmission blocks of the downlink subframes and then channels selection will be performed, and the UE will send the ACK/NACK response information using the format 1b with channel selection.
The most obvious advantage of the LTE-A system over the LTE system is that carrier aggregation is introduced in the LTE-A system, i.e., bandwidths of the LTE system are aggregated to obtain a greater bandwidth. In the system where the carrier aggregation is introduced, the aggregated carrier is called as a component carrier (CC), or is called as a serving cell. Meanwhile, concepts of Primary Component Carrier/Cell (PCC/PCell) and Secondary Component Carrier/Cell (SCC/SCell) are proposed. A primary serving cell and secondary serving cell are at least included in a system where the carrier aggregation is performed, wherein the primary serving cell is always in an activation state and the PUCCH is defined to be transmitted only on the Pcell.
In an LTE-A carrier aggregation system, when the HARQ-ACK response information is sent on the PUCCH, two sending methods are defined, PUCCH format 1b with channel selection and PUCCH format 3. For a UE which configures a plurality of serving cells, if the UE can support aggregation of only 2 serving cells at most, then the UE will send the HARQ-ACK using the PUCCH format 1b with channel selection when configuring the plurality of serving cells; if the UE can support aggregation of more than 2 serving cells, then when the UE configures the plurality of serving cells, a base station will further configure the UE through high layer signaling to determine whether the UE sends the HARQ-ACK response information using the PUCCH format 1b with channel selection or the PUCCH format 3.
The related carrier aggregation technology is applied to only FDD serving cells or TDD serving cells. In subsequent versions, considering the FDD serving cells and TDD serving cells, when the FDD serving cells and TDD serving cells are aggregated, how to send uplink control information is one of problems required to be solved urgently. Otherwise, the aggregation of the FDD serving cells and TDD serving cells cannot be achieved.